Practical applications for such a modulated laser beam include the study of the molecular (or atomic) properties of materials or other workpieces. Throughout this specification and claims the term "workpiece" will be used to cover simple materials, such as chemical elements or compounds, as well as more complex structures, such as electronic devices, that may be under study. When the workpieces studied include individual chemical elements or chemical compounds they may be in solid, liquid or gaseous phase.
The studied properties of the workpieces may include optical absorption characteristics; the lifetime or decay characteristics of various forms of luminescence, such as fluorescence or phosphorescence; photochemical or photophysical characteristics; the optical characteristics of electronic components, especially those used as optical detectors, such as photodiodes and photomultiplier tubes; and may also include electrical characteristics, such as the resistivity of an electronic component, e.g. a semiconductor, when such component is exposed to light.
Any of these characteristics may take the form of either or both of amplitude or phase variations with frequency. In a primary application according to the invention it is an objective to obtain details of these characteristics as a function of the frequency of light applied to the workpiece.
Other utilizations for a modulated laser beam according to the present invention include the measurement of distances including very short distances, e.g. between one micrometer and one meter, and the development of a frequency or phase modulated communications technique, as will be explained in more detail below.